Answers

2016-05-18T21:59:54+08:00
Use present and past in this problem.

This their present or current age:
Ping is x.
Loren is 3/4 x.

This is their age in the past or 4 years ago: 
Ping is x-4 --------------> 1st equation.
Loren is 3/4 x-4 -------> 2nd equation.
We subtract it to 4 because it is 4 years ago.

Multiply 1/2 to the first equation then put the 2nd equation be equal to them.
Solution:
1/2 (x-4) = 3/4 x -4
1/2 x - 2 = 3/4 x -4 -------------> Combine like terms.
3/4 x - 1/2 x = 4 - 2
1/4 x = 2
x = 2(4)
x = 8 ------> this is Ping's age now.

Subtitute x to Loren's age now:
3/4 x
= 3/4 (8)
= 24/4
= 6 -------> this is Loren's age now.

To find their age 4 years ago, subtract their age now to 4.  
Ping = 8-4 = 4 years old 
Loren = 6-4 = 2 years old

Answer: Ping is 8 years old and Loren is 6 years old now.


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